Active Transport -

The Na⁺/K⁺ pump restores resting membrane potential after an action potential. Inhibition (e.g., by ouabain) stops nerve signaling.

| Feature | Passive Transport | Active Transport | | :--- | :--- | :--- | | | None (kinetic energy) | ATP, light, or redox energy | | Direction | Down gradient (high → low) | Against gradient (low → high) | | Carrier proteins | Channel proteins or uniporters | Pumps, symporters, antiporters | | Equilibrium | Reaches equilibrium | Maintains steady-state disequilibrium | | Example | O₂ diffusion, water osmosis | Na⁺/K⁺ pump, glucose uptake in intestines | 3. Primary Active Transport Primary active transport directly couples a chemical reaction (e.g., ATP hydrolysis) to solute movement. 3.1 The Sodium-Potassium Pump (Na⁺/K⁺-ATPase) Located in the plasma membrane of animal cells, this pump is the archetype of primary active transport. It exports 3 Na⁺ ions out of the cell and imports 2 K⁺ ions inward per ATP hydrolyzed. This creates an electrochemical gradient: a high extracellular Na⁺ and high intracellular K⁺. active transport

SGLT1 in the small intestine absorbs dietary glucose. Patients with mutations in SGLT1 suffer from severe glucose-galactose malabsorption. water osmosis | Na⁺/K⁺ pump

The Mechanisms and Significance of Active Transport in Cellular Physiology glucose uptake in intestines | 3.